Indicators of Arm Fatigue

As we’re only 2 weeks away from the end of the high school season, I think it’s important to go over what we can visually see on the field and on paper when a pitcher is getting fatigued.

I would like to applaud the kids who gradually increased their chronic workload over the season. Here’s an example of the right way to do it:

Pre-Season Bullpens: 45/50 pitches

Scrimmages: 50/55 pitches

Weeks 1-4: 65/80 pitches

Weeks 5 and on: 70/90 pitches

*Maximal pitch limit for HS pitchers = 105

Think about the application of gradually increasing workload. Now, let’s compare this same application from the weight room to throwing.

If you took a few months off from training, and you try to go for your previous 1RM on a certain lift, there can be two scenarios that happen: either you get it or you don’t.

However, let’s say you do get the job done. Since your tissues are nowhere near as strong as they were previously, both producing force and recovering, you will probably feel pretty banged up for a few days.

The other scenario is not getting the job done. This is when you must stay humble and realize that your body is not where it used to be!

Now let’s take this example to throwing. If you took a few months off from throwing, and you try to throw a 70 pitch bullpen out of the gate, you’ll probably get the job done but your arm will be hanging for a week straight and your body won’t let you do anything else.

Okay, rant over now…assuming that you gradually increased your throwing volume over the course of the season, let’s dive into the research on how we can see the indicators of arm fatigue.

The Study

It has been hypothesized [1] that throwing velocity, accuracy, shoulder proprioception, and perceived soreness would all be negatively affected by fatigue.

To see if throwing specific exercise was the cause of the decrease in the variables mentioned, there was a group who went through a running workout as the “control”. This way, we can then make indirect-casual inferences.

The throwing group performed 10 pitches at 100% maximal intent with 10 seconds between each throw to “minimize the fatigue effect”. In reality, I think that pitchers get a bit more than 10 seconds, but this could be applicable if you’re just trying to quick pitch everyone!

However, this was only needed to collect accuracy data and average throwing velocity.

When the throwing group was going through the simulated game/throwing, 10 seconds were still kept between each pitch. The pitch count was totaled to 60 pitches.

The running group ran a 20-meter “beep test” until exhaustion.

What I do like about this study was the crossover design. Simply put, all participants did both the throwing and running protocols.

Immediately before and after whatever exercise they performed, they were asked to rate their perceived level of soreness in their throwing arm from 1-10. They were also asked to rate their level of perceived exertion using the Borg RPE scale (6-20).

But…what’s the difference between a 7 or an 8? A 7 and an 11?

Quick disclaimer: the Borg RPE scale is used for aerobic activity. Is throwing a baseball near maximal effort an aerobic activity? I will let you decide that answer here.

The Results

Mean throwing velocity was significantly reduced after the throwing and running protocols to a similar extent.

This result is particularly interesting because it goes to show how exhausting throwing can be. Especially with not a lot of rest in between pitches!

This also shows that throwing velocity itself is NOT the sole indicator of fatigue, since there was really no difference between the two protocols.

Throwing accuracy was significantly decreased after the throwing protocol, but not the running protocol. This makes sense because running does not require extensive use of the upper limb(s).

From a subjective measure, participants seemed to be more exhausted after the running protocol in comparison to the throwing protocol. Again, this makes sense because the running protocol was meant to put the participants in an exhausted state, hoping to find different results.

Participants also seemed to have an increase in arm soreness after throwing in comparison to running. Shocking (not really)!

These results, however, do show a time effect. The cross over design of the study allowed the investigators to make in inference on a cause and effect relationship.

In other words, changes in throwing accuracy and arm soreness were ONLY affected after the throwing protocol. Therefore, these two variables are better indicators of throwing fatigue.

Changes in Mechanics

Some research has shown that over the course of a game, pitchers will start to “over throw” and miss high in the strike zone. This has been attributed to a decrease in trunk flexion at ball release.

Other studies have shown that lateral trunk tilt, front-knee angle at ball release, and maximal external rotation all are significantly changed later in the game as volume is accumulated.

However, in this particular study, there was no difference in accuracy in the vertical plane. Rather, there was a greater difference in the horizontal plane (aka, hitting the black).

This study also showed there was no difference in shoulder proprioception after throwing. However, I believe this was because of the advanced methods they have used.

As a performance coach, when I treat my pitchers, I physically feel the difference in proprioception when I am performing manual arm care.

When the rotator cuff begins to fatigue, the strength and coordination of the muscles firing are delayed due to metabolite buildup in the surrounding joint area.

Therefore, it is critical for pitchers to maintain cuff strength, scapular strength, and tissue resilience/endurance during the season.